[news.eclipse.platform] How to create context sensitive menu ?

[Carsten Zerbst <automatic@xxxxxxxxxxxxx>]

Hello, 

I added some actions to the popup menu
and now want them to be context sensitive
depending on a state stored in my plugin. 

Is there an example available how to do this ?
As far as I understand I have to do this 
based on a system property ?

Thanks for any hint, Carsten